This invention relates generally to magnetic heads for recording and reproducing information or data on and from a magnetic recording medium, such as a magnetic recording tape or the like, and more particularly, the present invention relates to a perpendicular magnetization recording magnetic head with which magnetization is effected in a direction perpendicular to the plane of a magnetic recording medium.
Perpendicular magnetization recording technique has been introduced in order to increase the density of information to be recorded or written on a magnetic recording medium. Such a perpendicular magnetization recording method is disclosed, for instance, in U.S. Pat. No. 4,210,946. In a known technique for effecting perpendicular magnetization with respect to a recording medium, a magnetic head having a main pole and a sub or auxiliary pole is usually employed for magnetizing a small area on a magnetic recording medium such as a recording tape or sheet. The main pole is constructed of a thin magnetic layer or film, made of high permeability material, and a supporter made of a nonmagnetic material in such a manner that the thin magnetic film is sandwiched between a pair of nonmagnetic members constituting the supporter. The sub magnetic pole comprises a magnetic core equipped with one or more coils. The main and sub magnetic poles face each other and are spaced from each other so that a magnetic recording medium can travel through the space therebetween. Namely, the main and sub poles are arranged so that magnetic flux emitted from one end of the sub pole passes through the travelling recording medium to be received by the thin magnetic film of the main pole to constitute a magnetic circuit.
The main magnetic pole of such a perpendicular magnetization recording magnetic head is arranged to be in contact with the magnetic recording medium which moves in a given direction so that a predetermined contact pressure is given to the recording medium. Therefore, the recording medium and the contacting portion of the main pole of the magnetic head is apt to wear due to friction. In order to reduce such friction, it has been proposed hitherto, to use a lubricant in such a manner that a lubricant is mixed with the recording medium so that sliding friction with the head is reduced. According to another known technique for reducing such friction, the sliding surface of the recording medium is smoothed to provide a mirror finished surface. Similarly, for reducing the amount of wearing of the head various materials, such as hot press ferrite, Sendust, single-crystalline ferrite or the like, having a high resistance to wear are used.
The magnetic thin film of the main pole is sandwiched between a pair of nonmagnetic members as described in the above, while these nonmagnetic members of the main pole are made of ceramics, such as barium titanate, having a high resistance to wear so that it does not wear readily. However, such nonmagnetic members made of ceramics, glass, sapphire or the like, are not necessarily satisfactory because they cause damages in recording media. The wear of recording media results in the wear of the main pole in turn due to worn and therefore rough surface of the recording media.
Apart from the above described problem, there is another problem relating to the width of the thin layer of the main magnetic pole. Since the thin layer is interposed between a pair of nonmagnetic members of the supporter, the exposed end of the thin layer which comes into contact with the recording medium is apt to widen in the direction of the movement of the recording medium because the hardness of an adhesive adjacent to the thin layer is not as high as that of the thin layer. In addition, such an adhesive is apt to wear so that edges of nonmagnetic members of the supporter are apt to expose the recording medium to damage.
Furthermore, when making a plurality of tracks on a recording medium by a perpendicular magnetization recording magnetic head, there is a problem of crosstalk between adjacent tracks. To avoid such undesirable crosstalk, therefore, each track has to be spaced apart from adjacent tracks.
Furthermore, because of high pemeability the thin layer of the main magnetic pole of the head is apt to be influenced by an external magnetic field which may be emitted from some other magnetic devices. Such an external magnetic field results in the decrease in the output amplitude of the head.